1. Field of the Invention
The present invention relates to an ink-jet printer, in particular, an ink-jet printer capable of accumulating air bubbles generated in ink passages and discharging the air bubbles.
2. Discussion of Related Art
To assure a reduction in the size (the thickness) of an ink-jet printer, there is a demand for a reduction in the size (the thickness) of a carriage of the printer, in other words, there is a demand that the ink-jet printer is constructed in such a way that an ink tank which accommodates ink is not installed on the carriage. To this end, the ink in the ink tank which is installed on a main body of the printer needs to be supplied, via an ink supply tube, to a printing head carried on the carriage.
In the thus constructed ink-jet printer which uses the ink supply tube for supplying the ink from the ink tank to the printing head, the air inevitably permeates through the tube and is consequently dissolved in the ink due to properties or characteristics of the material for constituting the tube. Accordingly, it is needed to provide a bubble accumulating or retaining chamber on the upstream side of the printing head to remove the bubbles.
As a technique to remove the bubbles in the ink-jet printer which uses the ink supply tube, there is known an arrangement as disclosed in JP-A-2000-103084 (FIG. 1, in particular), for instance. In this arrangement, a manifold (functioning as the bubble accumulating chamber) is provided above the printing head while an ink tank and a circulating pump are provided on a stationary-position side, and the circulating pump is driven to remove the bubbles.
In the arrangement disclosed in JP-A-2000-103084, however, the ink-jet printer inevitably tends to be large-sized and complicated since it is needed to provide a return tube through which the ink is returned from the circulating pump to the ink tank for circulation.
Further, there is known an arrangement as disclosed in JP-A-2002-240310 (FIG. 5, in particular), for instance, that the air generated as the bubbles in the ink supply tube is accumulated at an upper portion of the ink tank installed on the carriage and is discharged by a discharge pump. After the discharge of the air, the ink tank is fluid-tightly closed by a discharge valve.
The applicant of this application proposed an air-discharging device 303 shown in FIG. 18, in the ink-jet printer constructed as described above. In the proposed air-discharging device 303, a valve member 302 is arranged to be moved within an air-discharge hole 301 which has a large-diameter portion 301A and a small-diameter portion 301B communicating with each other through a communication opening 301C and which communicates with a bubble accumulating chamber (not shown) through an upper recessed discharge-passage portion 308, such that the valve member 302 is moved in an axis direction of the air-discharge hole 301, thereby permitting the bubbles accumulated in the bubble accumulating chamber to be discharged. In this arrangement, an O-ring 304 (as a sealing member) for opening and closing the communication opening 301C has an inside diameter smaller than an outside diameter of a rod portion 302b of the valve member 302, so that, when the valve member 302 is moved upwards, the O-ring 304 is moved upwards together with the rod portion 302b. Further, for increasing the sealing tightness, there is provided a coil spring 305 which biases a valve head 302a in a direction in which the communication opening 301C is closed.
In the proposed air-discharging device 303, the coil spring 305 is inserted at its upper end potion on a supporting protrusion 306 in which an air-inlet 307 is formed. In this arrangement, the air introduced from the air-inlet 307 flows to the outside of the coil spring 305 through adjacent portions of the wire of the same 305, and is consequently discharged through the communication opening 301C.